This is South America’s premier Cup competition, something like the South American version of the Champion’s League. There are a few qualifying rounds where teams before the group stages. The group stages have eight groups of four teams. The four teams in each group play each other twice, once home and once away, and the top two teams of each group qualify for the next round. The competition runs from January (the qualifying rounds. Group stages start in February) and runs until June. The winner qualifies for the World Club Cup.
The number of teams that qualify from each country depends on the strength of that country’s league and the performance of its teams in the competition, just like in Europe. In 2017, Brazil sent a whopping eight teams! (six went straight into the group stages and two went into the qualifying rounds). Argentina sent five and Bolivia sent three. The winner of the previous year’s Copa Sul-Americana (which in 2016 was Chapecoense) also qualify for the competition and go straight into the group stages. Mexico isn’t in South America (everybody knows that, right?) but they are normally invited to participate every year. For some reason they didn’t send any teams this year.
For the latest results and fixtures, check out the dedicated Libertadores page.